The long-term objective is to develop strategies for cancer prevention and therapy by understanding the molecular basis of human cancer through studies of developmental and signaling mechanisms in model organisms. Zebrafish pancreas is used as a model organ to identify and characterize developmental regulators of cell fate and lineage determination, proliferation, survival, differentiation, morphogenesis and growth. A strategy has been developed to identify the genes that control various aspects of pancreatic organogenesis through chemical-induced mutagenesis screen that affect pancreas development in zebrafish. One (1)unique mutant, exocrine and pigmentation (eap), has small exocrine pancreas, normal islet and reduced skin pigment. Pancreatic duct branching is hypomorphic, and the acini are relatively small, whereas the acinar cells are differentiated but they contain relatively few zymogen granules. This data has led to our hypothesis that the epd mutation causes growth arrest of the exocrine pancreas. The epd gene product is expected to play a regulatory role in cellular proliferation of exocrine progenitors. The goal of this proposed study is to identify the epd gene by positional cloning technique. The first specific aim is to determine the chromosomal location of the epd gene based on simple sequence length polymorphism, and define the critical region harboring the epd gene by high resolution meiotic mapping. Clones from the BAG library as well as genomic contigs that span the epd locus will be identified. The candidate genes will be tested by gene knock-down using morpholinos to phenocopy the mutation, analyzing the gene mutation by PCR and DNA sequencing, and injecting the cDNA or mRNA to rescue the mutant phenotype. Molecular characterization of the epd gene will enable mechanistic study of its function by future experiments designed to test the hypothesis that epd controls proliferation of exocrine progenitors. These studies can be expected to provide further insights into the genetic regulation of pancreatic organogenesis and tumorigenesis. [unreadable] [unreadable]